In recent years, a humanoid robot and controlling walking operations of a humanoid robot has attracted the attention of a large number of researchers. A majority of research relating to the walking of the humanoid robot uses a ZMP (Zero Moment Point) norm. The ZMP norm controls the robot to keep a ZMP inside a supporting polygon. With this approach, the humanoid robot, and an ambient environment of the robot, may be modeled, and a differential equation may be solved. However, the modeling is difficult when there is an unknown factor. Furthermore, as it takes time to solve the differential equation, real time control of the robot is difficult.
As another approach, there is a method which does not use the ZMP norm. For example, there is an already known technology which, using a cyclic motion of a movable portion of the robot, adjusts phases of the cyclic motion in such a way that a posture of the robot stabilizes (for example, JP-A-2005-96068). Herein, a movable portion is a leg or arm of the robot.
Also, a technology is described in JP-A-2007-175809 which, while rendering unnecessary the modeling of the humanoid robot and the ambient environment of the robot, controls effectively in such a way that the humanoid robot may stably carry out various motions.
Also, a technology has also been developed which, in the event that an obstacle is placed on a walking surface, or in the event that there is an unevenness in the walking surface, controls the robot in such a way that the center of gravity of the humanoid robot becomes lower, in order to prevent the humanoid robot from falling over (refer to the description of U.S. Pat. No. 6,064,167).